The invention relates to a device for controlling a hydraulic actuator, comprising an electrically operated valve which controls the flow of pressure medium to and from the actuator, and comprising a controller, integrated into the housing of the valve or held on the latter in its own housing, for the position of the valve piston.
A device of this type comprising an electrically operated hydraulic valve is disclosed by DE 195 30 935 C2. A displacement sensor for the position of the valve piston converts the position of the valve piston into an electrical signal, which is supplied to a position controller as actual value. The controller for the position of the valve piston is arranged in its own housing, which is held on the housing of the valve. The controller ensures that the valve piston follows a position set point, which is supplied to the controller as an electrical input variable, for example in the form of a voltage. In this case, the position of the valve piston determines the magnitude of the passage cross section of the valve using valves of this type, flow of pressure medium to and from an actuator, for example a hydraulic cylinder, is controlled.
The document RD 30 131-P/10.99 “HNC 100 Series 2X” from Mannesmann Rexroth AG discloses a digital controller subassembly for electromechanical and electrohydraulic drives. Using a controller subassembly of this type, up to two different drives can be controlled independently of each other. The controller subassembly is provided for installation in a switch cabinet. A plurality of these subassemblies are preferably mounted together in a switch cabinet. From the latter there lead electrical signal lines for the transmission of set points to the drive and further signal lines, which are used for the transmission of actual values back from the drive to the controller subassemblies arranged in the switch cabinet. In the case of electrohydraulic drives, the controller subassemblies supply the set point for the position of the valve piston of an electrically operated hydraulic valve, which controls the flow of pressure medium to and from a hydraulic actuator. Various actual values, such as the position of the valve piston or the pressures in the area of the output connections of the valve, are fed back from the drive to the controller subassembly. This leads to an expenditure on circuitry which is not inconsiderable. Added to this is the fact that, because of the large number of electric lines which have to be connected in the switch cabinet, there is the risk of wrong connections during installation and during commissioning.